insert a placeholder for bullet (fixes #14)

quad/quadwriter/core.rkt

@@ -16,7 +16,7 @@
          "attrs.rkt"
          "param.rkt"
          "font.rkt")
-(provide para-break line-break page-break hrbr lbr pbr render-pdf)
+(provide para-break line-break page-break bullet-quad hrbr lbr pbr render-pdf)
 
 (define-quad string-quad quad ())
  
@@ -273,6 +273,8 @@
 (define (make-hr-quad line-q)
   (struct-copy quad line-q [draw-start hr-draw]))
 
+(define bullet-quad '(q ((special "bullet"))))
+
 (define ((finish-line-wrap line-q) pcs-in opening-q ending-q idx)
   ;; we curry line-q so that the wrap size can be communicated to this operation
   ;; remove unused soft hyphens so they don't affect final shaping

quad/quadwriter/tags.rkt

@@ -103,4 +103,4 @@
 
 (define-tag-function (ol attrs exprs) (list-base attrs exprs))
 (define-tag-function (ul attrs exprs) (list-base attrs exprs "•"))
-(define-tag-function (li attrs exprs) (qexpr attrs exprs))
+(define-tag-function (li attrs exprs) (qexpr attrs (cons bullet-quad exprs)))